Low profile micro-Winchester disk drives are known. In addition to the related patents listed above, a representative low profile disk design is disclosed in U.S. Pat. No. 4,965,684 to Stefansky, entitled "Low Height Disk Drive". The architecture employed in the Stefansky patent employed "embedded servo" head positioning techniques wherein a multiplicity of embedded servo sectors provided, inter alia, head positioning information to the head positioner structure. The obvious drawback of the embedded sector approach is the overhead associated with the multiple servo sectors, an overhead which limits the overall data storage capacity of the disk drive.
One known way of avoiding the overhead associated with embedded servo sectors is to include an optical encoder for providing coarse head positioning information to the head positioner structure. This technique is followed in the teachings of the referenced U.S. Pat. Nos. 4,772,974 and 5,005,089, noted above. Improvements described in the referenced U.S. patent application Ser. No. 07/556,945 of Thanos et al, filed on Jul. 20, 1990, entitled "Head Position Recalibration for Disk Drive", now U.S. Pat. No. 5,227,930, enabled a low profile (one inch high) micro-Winchester disk drive employing an optical encoder to achieve a data storage capacity of approximately 52 megabytes of user data per data storage disk.
While the approach set forth in related U.S. Pat. No. 5,227,930 worked well, and has been very successful commercially, a hitherto need has remained to improve the capacity and performance of the disk drive described therein, so that as much as 120 megabytes of data may be stored on both sides of a micro-Winchester data storage disk, and so that practical access times to the vastly expanded data capacity are reduced.